CORRECTED - Sanofi on track for 75.3 mln H1N1 US vaccine doses

* Production on track with HHS agreements

* Vaccine yields now running above expectations

* No expectations for future production problems

(Makes clear in first paragraph that Sanofi is on track; eliminates reference in second paragraph to production problems)

By David Morgan

WASHINGTON, Oct 23 (Reuters) - U.S. health officials are struggling to deliver vaccine against the H1N1 pandemic virus ahead of its spread but Sanofi Pasteur (SASY.PA), one of five vaccine makers under contract, said on Friday it was on track.

A spokeswoman said the company could now deliver 75.3 million doses of bulk vaccine ingredients by December.

"Our shipments are tracking close to what we have agreed to with (the U.S. Department of Health and Human Services). Thus far we have provided more vaccine to HHS than all other manufacturers combined," Sanofi, the vaccine unit of Sanofi-Aventis SA, said in a statement.

Sanofi said it has shipped 12 million of the 16.1 million vaccine doses the U.S. government had received as of Friday.

"We have orders for 75.3 million doses of bulk antigen for anticipated delivery between October and December. We are on track to deliver this by December," the statement said.

HHS has also ordered vaccine from CSL Ltd (CSL.AX), Novartis AG (NOVN.VX), GlaxoSmithKline (GSK.L) and AstraZeneca's (AZN.L) MedImmune unit.

U.S. health officials recently trimmed supply expectations for H1N1 swine flu vaccine by 25-30 percent for October, saying manufacturers had run into production problems.

The delay has caused vaccine shortages at U.S. immunization clinics at a time when H1N1 flu activity has become widespread in 46 states.

Much of the available vaccine has been MedImmune's nasal spray, which contains live virus and is not recommended for some people at risk, including children under 2, pregnant women and children and adults over 50.

Companies are using decades-old technology used to make seasonal influenza vaccine to manufacture the H1N1 immunizations, but this involves uncertain methods that start with growing the virus in chicken eggs. For some reason H1N1 did not always grow well.

MedImmune had no problems but the other companies did.